1. Field of the Invention
The invention relates to a system for transmitting television picture information by means of a first series of coefficients of a second series of transformation functions in which the television picture information is transformed subpicture-wise, said system comprising a picture converting device which comprises a transformation device for the subpicture-wise transformation of the television picture for supply to a transmission medium, and a display apparatus which is connected to the transmission medium and which comprises a decoder for reconstructing, from the subpicture-wise organized first series of coefficients, the television picture information organized in television lines and in pixels within a television line for the purpose of display. The transmission medium may be a communications channel, for example, a bundle of telephone lines, or a storage medium, for example, a magnetic tape within a video cassette recorder (VCR).
2. DESCRIPTION OF THE PRIOR ART
A system for performing such transformation is disclosed in an article by H. Bacchi et al, Real-time orthogonal transformation of colour-television pictures, Phillips Technical Review, Volume 38, 1978/79, pages 119-130. Such encoding serves to limit the redundancy of the picture information so that the bit rate in a communications channel, or the number of bits to be stored in a storage medium may be, for example, a factor four smaller without the subjective display quality being substantially reduced. For the transformation functions, use is preferably made of Hotelling, Fourier, Hadamard and Haar functions; in the following example only Hadamard functions and matrices are considered, because they allow for simpler arithmetical operations. The reduction of the redundancy leads to a higher susceptibility to errors. Certain errors are subjectively experienced as being hardly annoying and other errors are very annoying. It is the object of the invention to enable correction in the coefficients pertaining to a single subjective of at least one bit error in a first number of important coefficient bits, and at least one further bit error in a selection of very important coefficient bits from said first number, without utilizing excessive redundancy and hence without substantial addition of equipment.